A multi-output DC-DC converter has been known that includes multiple output systems among which output systems other than one output system are provided with p-MOS switches. The output voltage of the output system provided with no p-MOS switch is the maximum among the output systems of all the output systems. Consequently, the p-MOS switches provided for the other output systems can be turned off using this output voltage.
It is assumed that the output system provided with no p-MOS switch is called an output system 1. If the output voltages of the output systems other than the output system 1 are increased to be at least the output voltage of the output system 1, the output voltage of the output system 1 is also increased accordingly. Furthermore, the output voltage of the output system 1 cannot be reduced to be less than the output voltage of the other output.
To eliminate the limitation among the output voltages, it can be considered that the output system 1 is connected to no external load but is used as an output system dedicated for driving the gates of the p-MOS switches. Unfortunately, in this case, a diode, an output terminal and a capacitor are required only to drive the gates. This requirement increases the circuit area and, in turn, increases the cost.